The present invention relates to an energy transmission device having a connection unit for connecting an electrical energy source or an electrical energy sink and a transmission member which is electrically coupled to the connection unit and can be electrically coupled to a second transmission member for transmitting electrical energy.
The present invention further relates to an energy transmission system having a first energy transmission unit and a second energy transmission unit which can be electrically coupled to the first energy transmission unit in order to transmit electrical energy.
In the field of motor vehicle drive technology, it is universally known how an electrical machine is used as the sole drive or jointly with a drive motor of a different type (hybrid drive). In such electric or hybrid vehicles, electrical machines are typically used as the driving motors which are supplied with electrical energy by an electrical energy storage, such as, for example, a battery. The electrical energy storages of electric vehicles or plug-in hybrid vehicles have to regularly, depending on the charging state, be connected to a public energy supply in order to charge the energy storage with electrical energy.
A cable can, for example, be used to transmit electrical energy from a charging station to the vehicle. Such a cable connection is however not very user friendly and furthermore represents a possible danger to the user because said user could come into contact with live parts if the plug connection or the cable is damaged.
As an alternative to the cable connection, there is the option of supplying the vehicles with electrical energy via a wireless energy transmission. In the case of an inductive energy transmission, an alternating magnetic field is generated on the primary side with the aid of a coil. At least a portion of said alternating magnetic field penetrates a secondary side which likewise has a coil. A voltage is thereby induced in the coil of the secondary side, and energy is thus transmitted from the primary side to the secondary side. The coil system of the primary side and the secondary side can therefore be modelled as a transformer with a large air gap. The air gap causes large leakage inductances and a relatively poor coupling between the primary and the secondary coil. The leakage inductances lead to high reactive currents in the system which do not contribute to the transmission of energy but produce ohmic losses. For that reason, the efficiency of the wireless energy transmission is worse than that of the cable-based transmission. Nevertheless, such an energy transmission is more user friendly due to the ease of use thereof and therefore enjoys greater acceptance among users.
Operational reliability represents an important topic in systems employing wireless energy transmission. During the energy transmission, a magnetic field of high field strength and flux density is thus built up in a region between the primary side and the secondary side. If, for example, magnetizable dust particles or contaminants are located in this gap, said particles or contaminants are then heated up dramatically by the induced eddy currents. As a result, the magnetizable dust particles or contaminants are released as glowing material in an area surrounding the wireless energy transmission and thus endanger people and objects in this area. Wireless energy transmission devices can therefore not be used in environments in which such magnetizable dust particles or contaminants occur (for example iron ore mining operations, metal workshops, steel plants etc.)